1. Field of the Invention
The present invention relates to a stage construction incorporating a movable stage whose position can be fixed, which is used in a semiconductor exposure device or in a sample analysis device such as a photoelectron spectroscopy device, an X ray microscope, an electron microscope, or the like.
2. Description of the Prior Art
When performing exposure of a wafer using a semiconductor exposure device, it is necessary to fix the position of the wafer accurately with regard to its six spatial degrees of freedom, conventionally designated as X, Y, Z, .theta., .alpha., and .beta.. Further, in a photoelectron spectroscopy device, an X ray microscope, an electron microscope, or the like, in the same manner it is necessary to fix the position of the sample for analysis accurately with regard to its six degrees of freedom. In this field, in the prior art, assemblies of stages with 1-axis movement, 2-axis movement, or 3-axis movement have been superposed in combination as required, so that the combination can be utilized as a six axis stage construction. Such stages achieve the desired accuracy of position fixing by incorporating suitable assemblies, including driving mechanisms such as linking mechanisms, ball screws, planetary screws, linear screws, or the like, speed reducing mechanisms such as gears or the like, and friction bearings such as cross roller guides, V-flat sliding groove guides and the like.
However, reduction in mass is difficult to realize for such prior art stage constructions, due to the bulk of the main body of the stage construction becoming large. Accordingly the inertia of the movable parts of such a stage construction becomes great, so that it is difficult to increase the speed of their movement, and also improvement of the accuracy of position fixing becomes difficult. Further, due to the existence of at least two faces which are in sliding mechanical contact, one upon a fixed stage and one upon a movable stage, the cleanliness of the environment provided by such a stage construction is inevitably deteriorated due to generation of dust from the movement mechanism. Yet further, if the stage construction is to be used under high vacuum conditions, the problem arises that the vacuum level will be reduced, since lubricant needs to be used between these mechanically contacting faces.
In order to implement non-contact operation of such a stage construction, it is possible to levitate the movable stage by floating it upon air bearings, and to drive it using a linear motor; but the cleanliness of the environment is degraded since the air gushing out from the air bearing will inevitably stir up dust, and for example the yield rate of a semiconductor process utilizing this stage construction is deteriorated. Furthermore, due to the use of a flow of air for levitating the movable stage, it is fundamentally impossible to apply this expedient to a stage which is intended to operate under vacuum conditions.